Phantom loading-coil.



UNITED STATES PATENT OFFICE.

WILLIAM FONDILLER, OF NEW YORK, N. Y., ASSIGNOR T0 WESTERN ELECTRIC COM- PANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

PHANTOM LOADING-COIL.

Specification of Letters Patent.

Patented June 26, 1917.

Application filed May 1, 1916. Serial No. 94,695.

To all whom it may concern Be it known that I, WILLIAM FoivnILLER, a citizen of the United States, residing at New York, in the county of New York and State, of New York, have invented certain new and useful Improvements in Phantom Loading-Coils, of which the following is a full, clear, concise, and exact description.

This invention relates to phantom circuit loading in telephony, and in particular to a loading unit by which inductance is added simultaneously to a pair of physical circuits and to a phantom circuit derived from them. Its ob ect is to secure this simultaneous loading in an efiicient manner, to increase the magnetic stability of the loading unit, and to provide for any desired ratio of phantom circuit inductance to physical C11- cuit inductance.

These objects are accomplished by providing suitably proportioned gaps of high reluctance in the cores of the coils used for physical circuit loading, and by the use of magnetic bridges of low reluctance arranged to operate in conjunction with the gaps to secure the desired flux distribution due to phantom circuit currents.

The manner in which these objects are ac- I complished will be further explained in connection with the drawings, in which Figure 1 represents a circuit diagram of the two physical circuits and the phantom circuit, including the loading unit; and Fig. 2 is a perspective view of the magnetic structure of the loading unit.

Referring to Fig. l, l and 2 represent two physical circuits which are loaded by including in them inductance coils whose windings are mounted on the semi-toroidal cores 3 and 4;. 5 is a hantom circuit derived from these as usual y employing the line conductors of each physical circuit in parallel as one effective conductor of th phantom circuit. In magnetic structure, 6 represents a gap or an equivalent break in the magnetic circuit, formed in this case by introducing a strip of non-magnetic material. This material should also obviously be non-conducting to avoid loss of energy in eddy currents.

The two loading coil cores are placed in this invention one above the other, in the manner illustrated in Fig. 2. In this latter figure, 6 represents the strip of separating material described in connection with Fig. 1, and 7 yokes of magnetic material, preferably laminated iron, used to form a magnetic bridge of low reluctance to connect the cores of the inductance coils. These magnetic bridges 7 are shown in section in the first figure and are indicated by the same characters.

The operation of the system is as follows:

When currents flow in opposite directions in the two conductors of the physical circuit 1, for example, a magnetic flux is produced which lies in circular paths around the core 3, as is usual in loading of telephone lines. The windings areso arranged, however, that when currents in the conductors of circuit 1 flow in the same direction, as will be the case in phantom operation, north and south magnetic poles will be produced at 8 and 9,'respectively, at a given instant, and at the same time south and north magnetic poles at the points 10 and 11 respectively. As a consequence of this, the lines of phantom circuit flux will lie in the two halves of cores 3 and 4 in arallel and Will be completed in the magnetic bridges 7. In the first of these cases, namely, that of physical circuit operation, the resultant flux will be linked with the physical circuits only, and in the second with the phantom circuit only; and consequently, the operation of these circuits will be independent.

It has been found that the method of loading phantom circuits which depends solely upon employing a leakage field, is subject to the objection that it is diflicult to secure a sufiiciently high phantom circuit inductance for a given physical circuit inductance, and it has also been found that the use of loading coils without gaps renders them liable to magnetization by lightning discharge or other heavy currents. Both of these objections are overcome in this invention by the use of gaps, for these add stability to the magnetic circuit and also provide for increasing the reluctance of the paths traversed by the physical circuit flux to any desired value, without increasing the reluctance of the path traversed by the phantom circuit flux.

The semi-toroids 3 and 4 may be of any suitable magnetic material. In practice, it

has been found desirable to make them of finely divided iron, the individual particles of which are coated with a thin insulating film, the core structure being formed under high pressure, in the manner described and claimed in an application for patent Serial No. 89,409, filed'April' 6, 1916, by James B. Speed, and assigned to the same assignee on the present application. The laminations for the magnetic bridges 7 may be stamped from sheet metal, or may also be of finely divided iron, molded under high pressure. It Will be understood that the term toroid,

as used herein, is intended to refer to a ring of any desired cross-section; and that instead of rings, rectangular or other forms of frames might be employed, and that, for Want of some broader expression, the term toroid is used to denote all sucn structures.

What is claimed is:

1. A loading unit adapted for use With- Copies of this patent may be obtained for and two physicalcircuits and a derived phantom circuit comprising cores with gaps of high reluctance therein, windings on said cores adapted for inclusion in-each of the conductors of said physical circuits, and two bridges'of low reluctance joining said cores, the lengths of said gaps and the magnetic reluctance of said bridges being adjusted'to secure a' desired ratio of phantom circuit inductance to physical circuit inductance.

3. A loading unit core structure comprising two toroidal core members, bridges of low reluctance between said members at diametrically opposite points, there being a gap; ofhigh reluctance' transversely interseating. each of said toroidal members.

4. A loading unit core structure comprising two toroidalcore members, bridges of lowreluctance-between said'members at diametrically opposite points, there being a gap of high reluctancetransversely intersect 111 each of said toroidal members and longitudinally bisecting said bridges.

Iii-Witness whereof, I- hereunto subscribe my name this-29th dayof April'A. D., 1915.

WILLIAM? FONDI-LLER:

five cents each, by addressing-the Commissioner of Patents; Washington, D. C. 

